Microstructure and corrosion resistance of induction melted Fe-based alloy coating

Abstract Two kinds of induction melted Fe-based alloy coatings with chemical compositions (in wt.%) Fe–30.4Cr–3.5B–3.1Si–20.3Ni–8.7Co–3.6Mo–2.7Cu (C +) and Fe–44.1Cr–5.6B–4.7Si (M) deposited onto Q235 steel by ultrasonic frequency inductive cladding (UFIC) technique have been investigated in terms of microstructures, phase composition, microhardness and corrosion behavior by SEM/EDS, XRD, Vickers microhardness tester and Raman spectroscopy analyses. The results showed that four morphologies of austenite γ-Fe, eutectics γ-Fe/(Cr,Fe) 2 B, borides (Cr,Fe) 2 B and precipitations enriched in Mo contained in the C + coating whilst ferrite α-Fe, borides Cr 1.65 Fe 0.35 B 0.96 and eutectics α-Fe/Cr 1.65 Fe 0.35 B 0.96 were identified in the M coating. EDS line analysis of the interdiffusion zone indicated that element Fe decreased from the substrate into the coating while that of Cr and Si was in the reverse due to the dilution of the substrate. The average microhardness value of the M coating was higher than that of the C + coating, which was ascribed to the higher volume content of borides uniformly dispersed in the matrix. Due to the formation of the protective oxidation layer formed onto the coating, the corrosion resistance of both coatings increased over one order of magnitude compared with the substrate by the immersion and electrochemical tests in a 3.5 wt.% NaCl solution.